Colloidal adhesive composition



Patented May 3, 1927.

BRADLEY DEWEY. OI CAMBRIDGE, MASSACHUSETTS,

ASSIGNOB TO DEWEY AND ALMY CHEMICAL COMPANY, OI CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MAS- SACHUSET'IS.

COLLOIDAL ADHESIVE COMPOSITION.

No Drawing.

This invention relates to adhesive emulsions or the like; an object of this invention is to provide colloidal substances,- emulsions and the like, wherein the ultimately adhesive particles in internal or disperse phase shall be physically sub-divided or extended, preferably without chemical disintegration or cleavage of theultimate characterist c molecular constitution thereof, and wherein the inherent natural adhesive properties of such substances may be rendered more useful by reducin the cohesiveness of the particles among t emselves.

It is also an object of the invention to provide a compositlon wherein the inherent adhesive qualities of the colloidal substance are developed to a maximum degree of practical usefulness, with corresponding economies of the amounts require The invention is characterized by a treatment of a closely associated aggregate of particles with an extending col oid preferably in the resence of a liquid in which both the particles and the extending colloid are freely miscible.

As typical examples of substances, which exemplif the invention, may be cited rubber latex an a colloidal earth, such as bentonite cla V i ith rubber latex, which may be defined as a water emulsion of natural or synthetic origin, of rubber globules, it may be readily observed that a considerable portion of such globules possesses appreciable adhesiveness while wet and of moderate concentration, but that this property is substantially restrained or overcome by dilution.

This is due in part to the inevitable effect of dilution but perhaps more to absorption of the discrete particles when distributed over a slightly porous surface. Ifor example, ordinary natural latex containing approximately 35% of rubber substance may serve as an adhesive for such purposes as the attaching of labels, but the fact that ordinary naphtha or benzol cements containing approximately 5 or 6% of rubber serve this purposeindicates that higher concentrations of rubber are not necessary. However, if rubber latex is diluted to a rubber content of such small proportion the discrete particles appear to penetrate or to be absorbedby any slightly porous surface thus nullifymg the adhesive properties of the particles.

Application filed November 14, 1924. Serial' No. 749,998.

On the other hand, a rubber emulsion containing approximately 35% of rubber is expensive an furthermore, because of the co eslve nature of the particles between themselves, when dried, the efiectiveness of their adhesive properties for many urposes is materially impaired. For examp e, when labelllngtin cans with latex the cohesion of the particles among themselves is greater than thelr adhesion to the tin plate and consequently it is often easy to strip the label from the can. This is articularly true if there is a thin film of oil on the tin plate.

Whatever the theoretical or precise explanation, however, the empirically observed characteristics of latex are those of a liquid having extremely minute particles or globules of rubber substance uniformly dispersed therethrough which are inherentl adheslve and which upon evaporation or c emical treatment agg omerate into a cohesive mass of marked tensile strength and elastlcity, ture.

Bentonite, clay and exhibits to an optimum degree the characteristics desirable in the extendin or dispersing mediums suitable to be use in the invention, is a finely divided colloidalearth capable of existing as a powder in moist air but evidencing an extreme avidity for water when contacted therewith in li uid phase, with concurrent conversion to-a uid colloidal gel. Such conversion is probably due to adsorption of the water b the clay particles, or vice versa, but actual chemical h dration may also occur simultaneously.

he resulting gel occupies many times the volume of the original powder and exhibits and essentially homogeneous in struca relatively high degree of plasticity, with plastic flow taking place under a slight superimposed pressure. It is homogeneous and freely miscible in large proportions with water, though with eventual separation into a heavier portion which precipltates and an apparently permanent colloidal suspension. It is further characterized by its facility of wetting and spreading or flowing freely upon surfaces to which it may be applied, without substantial pressure being required and without interruption of its continuity, even in thin films.

As a specific and typical example of the invention, the treatment of rubber latex emulsion with bentonite clay, in the presence of water, will be now described.

A water emulsion of uncoafgulated rubber, such as natural rubber latex ro tree, and ordinarily containing 35% more or less of rubber solids is found to be suitable for this purpose. This may COIltll1I l' B' relatively high proportion of solids to facilirate shipment by a reduction of unnecessar weight and bulk, but may be diluted wit water to the degree desired.

A colloidal suspension of bentonite 1n water is also prepared as by adding the bentonite to water with continuous agitatlon.

The colloidal gel thus prepared 1s thoroughly mixed with the desired quantity of rubber latex. The relative proportions of the in redients, colloidal earth (bentonite) and ru ber in water emulsion (latex) while susceptible of variation are to be such that the latex particles, ultimately depended on for adhesive purposes, are dispersed through a predominant quantity of bentonite-which when dry is not at all adhesive. Of the two, bentonite is the continuous and latex the occasional substance, though the latter, by reason of its subdivision is of frequent occurrence in the composition. Both are extended in the fluid medium (water) so that an easily applicable material is rovided, capable of being thinly spread, leaving when the water has evaporated a film predominantly composed of bentonite and having adhesive latex particles scattered through it. The order or condition in which the several elements are combined may be modified in accordance with conditions of transportation and practice. In the event that a paste-like consistency is desired, for example, the following quantities have proven especially satisfactory:

18 lbs. bentonite lbs. water, 10 lbs. of 35% rubber latex emulsion.

The recommended manner of combination is, first, to soak the bentonite in the water for a time suflicient to produce a paste of uniform consistency, and then to stir the paste and latex emulsion together.

The precise mechanism of the association of the two substances-obviously does not lend itself to exact determination and can not therefore be described nor defined with conclusive accuracy; The characteristics of the resulting composition, however, indi cate that the latex globules have become uniformly extended or disseminated throughout the fluid colloid medium and that they are carried with it, without segregation, even when spread into extremely thin films and the like. Although the mixture so produced does not exhibit a marked degree of adhesivenes's, while in the wet or fluid condition, it develo s an efi'ective adhesion in the course of; ry'ing, which is especially manifestin th n film's.

m the rubber well as paper, smooth-finished cloth, leather 'etc'. Consequently it finds an extensive and peculiarly appropriate application in fixing labels and the li e to metal and glass surfalices, though it is adapted for other uses a so.

' The paste is capable of extension to extremely thin films which are nevertheless strongly adhesive. Accordingly a small amount only is required. But what is of greater importance, the thin film is spread readily and uniformly and en uently dries rapidly. On the other hand, w ile in relatively thick volumes, the contained moisture does not evaporate ra idly and consequently does not deteriorate uring the normal period of application.

The adhesive qualities of such a preparation are made available to the fullest extent through the action of various phenomena. In the firs't place the suspended bentonite raises the plasticity of the paste to such a point that no appreciable amount of rubber is removed from its sphere of action one. surface by absorption or by penetration. Secondly, in the dried mass the bentonite serves to keep apart the individual discrete particles of rubber and to allow them to. exert their adhesive action without cohering sufiieiently to promote stripping, and thirdly it is thought that the bentonite, due to its highly absorptive characteristics tends to remove by blottin action some of the greasy film often foun on tin plate thus promoting adhesion of theadhesive to the tinned surface. y

The voluminous character of the colloid described makes possible an extremely wide dissemination of the latex particles therethrough, the retention of such spaced relation while the composition is in its fluid condition, and a considerable reduction in volume or area, upon complete evaporation of the liquid medium in which it is carried. Consequently, wide limits of dispersion are possible though preferred ranges will be selectively determined b the properties of the materials used and t e conditions under which the product is to be employed.

Should it be necessary or desirable to add a preservative 'to theadhesive composition, the following formula will prove effective: fluid ounce chloroform, 5 fluid ounces toluol, 5 fluid ounces oil of cloves.

The oil of cloves serves predominantly as a maskin odor, though it. possesses preservative ua ities also.

Wit the addition of such preservatives or others which may be found to be equivalents therefor, the composition while not otherwise aifected, may be prepared in quantity and stored or shipped tances without deterio putrefaction, even afte I been opened repeatedly I claim:

1. An adhesive com dominating substantially in quantity over 10 at disthe rubber. I ration an without 2. An adhesive composition comprising r the container has bentonite and latex, bot extended in water,

the bentofiite predominating substantially in quantity over the latex. position comprising, Signed by me at Boston, Massachusetts,

during use.

colloidal clay in suspension and rubber m' this 13th day of November, 1924.

emulsion in water, the colloidal clay pre- BRADLEY DEWEY. 

